Fertilizing capacity of bovine spermatozoa selected after swim-up in hyaluronic acid-containing medium

Abstract

Hyaluronic acid (HA) was used to select spermatozoa from frozen-thawed semen from five bulls; two were highly fertile and three had low fertility related to low post-thaw motility of the spermatozoa. Spermatozoa were collected after 1 h of self-migration in one of two media: a modified Tyrode's lactate solution (TALP) or a medium consisting of equal volumes of TALP and phosphate-buffered saline to which HA was added to obtain a final concentration of 1 mg mL-1 (HA medium). The selected spermatozoa were used to inseminate oocytes matured in vitro at a concentration of either 1.0 x 10(6) or 0.5 x 10(6) mL-1, constituting a 5 x 2 x 2 factorial experiment. After 19-22 h of sperm-oocyte co-incubation, fertilization of oocytes was assessed. The two concentrations of spermatozoa differed significantly in the percentage of oocytes penetrated (P = 0.001) and the percentage of oocytes with two pronuclei (P = 0.002). When 1.0 x 10(6) mL-1 spermatozoa were used, spermatozoa collected after swim-up in the HA medium fertilized more oocytes (P = 0.01) than did those collected after swim-up in TALP. Variation between bulls was also significant (P = 0.002). The beneficial effect of the HA medium was more evident in the group of low-fertility bulls (P < or = 0.03), where neither the variation between bulls (P > or = 0.06) nor the interaction between the methods of sperm selection and bulls (P > or = 0.10) was significant.(ABSTRACT TRUNCATED AT 250 WORDS)